Lubricating oil



Patented July 4, 1939 UNITED STATES PATENT OFFICE 2,164,393 LUBRICATINGon. 9

Elliott Alfred Evans, LondonQEngland, asslgnor to C. C. Wakefield &Company Limited, London, England, a British. company No Drawing.Application April 14, 1936, Serial 12 Claims.

This invention is for improvements in or relating to lubricants whichare to be used under conditions which tend to disrupt the lubricantmechanism.

film-rupture of about 3,000 to 4,000 pounds per square inch.

These extreme-pressure lubricants originally consisted of lubricatingoil which contained sulphur, either in the form of flowers of sulphur oras a colloidal dispersion. The sulphur, however, was liable toprecipitation and it was later proposed to prepare theseextreme-pressure lubricants by treating a fatty oil, for example ananimal oil, with thionylchloride or with similar reagents, such assulphur monochloride, sulphur dichloride etc., and then adding theproduct of this reaction to a mineral oil.

The theory as to the action of extreme-pressure lubricants has been thatthe sulphur reacts with metallic surfaces and forms a very thin coatingof iron sulphide and that this sulphide film is sufficient to preventthe metallic surfaces coming into contact with one another should thelubricant film be ruptured. If this theory is, in fact, correct, then itis obvious that the sulphur contained in the oil must be in such form asto be capable of reacting with the metallic surfaces which it is desiredto lubricate. On the other hand, the sulphur compound must not be soreactive as to induce corrosion of the surfaces.

It was found, however, that with these prior processes no set conditionscould be determined which would ensure a uniform product always beingobtained and it was therefore always necessary when preparing anextreme-pressure lubricant to apply the method of trial and error inarriving at a satisfactory composition.

It will be appreciated, therefore, that in order In Great Britain April15, 1935 to overcome these difficulties it is desirable to utilise asfar as possible definite compounds, of high purity, in order thatreproducible'results may be obtained without resorting to the. laboriousand probably inaccurate method of trial and error.

According to this invention an extreme-pressure lubricant comprises alubricating oil or grease having dispersed therein a small quantity of athin-ether. It has been found that the desired effects may be obtainedby employing the thioether in quantities up to about 2% by weight oftheoiL I A feature of the invention consists in that the-thio-ethercomprises two aromatic radicals. Preferably, at least one of saidaromatic radicals contains either a hydroxyl substituent or a carboxyl(or ester) substituent.

A further feature'of the invention consists that each of said aromaticradicals contains both a hydroxyl substituent and a carboxyl (or ester)substituent. Preferably, the hydroxyl substituents'are located. in thepara-position in the aromatic-radical.

A stillifu" her feature of the invention consists inthat said thio-ethercontains two aliphatic radicals. Either one or both of said aliphaticradicals contains either an hydroxyl substituent or a carboxyl (orester) substituent or both.

In one preparation which is given by way of example, a mixture of 50grams of thionylchloride and 30 grams of methyl-salicylate was placed ina 300 cc. flat-bottomed flask and 20 grams of copper dust were thenslowly added. The reaction which then takes place is accompanied by theether.

00cm 00cm When 0.5% of this pure compound was added to a pure mineraloil, the film-rupture strength was found to be raised to the extremelyhigh value of 15,000 pounds per square inch, a remarkable increase overthe value obtained with the puremineral oil which, in the Almen tester,gave a film-rupture strength of between 3,000 to 4,000 pounds per squareinch. The extreme-pressure lubricants hitherto prepared have in generalrequired at least 5% of a sulphur base (prepared by reacting sulphurchloride with the fatty oil) in order to produce a comparable increasein the film rupture strength of the oil.

Other compounds which may be employed are those obtained, in ananalogous manner to that described above, from ethyl benzoate and ethylphthalate which when used in a mineral oil in quantities of 1% haveyielded lubricants having a film-rupture strength of 14,000 and 12,000pounds per square inch respectively. {The thioether prepared, in asimilar manner to that described above, from ethyl crotonate when addedto a mineral oil in the proportion of 1% by weight yielded a lubricanthaving a film-rupture strength of 11,000 pounds per square inch. It willbe understood that the thio-ethers may be prepared by any suitablemethod, for example,

they may be prepared by reacting sulphur mon0-' chloride or sulphurdichloride with the aliphatic or aromatic compounds instead of thionylchloride.

The invention also includes within its scope, the method of preparingextreme-pressure lubricants which comprises dispersing thio-ethers ofthe above-mentioned class in a lubricating oil or grease in quantities,which are accurately controllable.

It will also be appreciated that the invention is not restricted to theemployment of particular proportions of the thio-ethers since withincertain limits the film-rupture strength of the lubricant may beadjusted to a desired value in accordance with the quantity ofthio-ether added in order to render the lubricant suitable for anyspecial use or mechanism.

I claim:

1. An extreme-pressure lubricant comprising a lubricant having dispersedtherein between 0.1% and 2% of a thio-ether comprising two aromaticradicals at least one of which aromatic radicals contain an estersubstituent.

2. An extreme-pressure lubricant comprising a lubricant having dispersedtherein between 0.1% and 2% of a thio-ether comprising two aromaticradicals at least one of which aromatic radicals contains an hydroxylsubstituent and an ester substituent.

3. Anextreme-preSsure lubricant comprising a lubricant having dispersedtherein between 0.1% and 2% of a thio-ether comprising two aromaticradicals at least one of which aromatic radicals contains an hydroxylsubstituent in the paraposition and an ester substituent.

4. An extreme-pressure lubricant comprising a lubricant having dispersedtherein between 0.1% and 2% of a thio-ether comprising two aromaticradicalsboth of which aromatic radicals contain an hydroxyl substituentin the para-position and an ester substituent,

5. An extreme-pressure lubricant comprising a lubricating oilhaving-dispersed therein between 0.l% and 2% of a thio-ether having anester-substituent.

6. An extreme-pressure lubricant comprising a mineral lubricating oilhaving dispersed therein up to 2% of bis (B-carbomethoxy4-hydroxyphenyl) thio-ether.

7. An extreme-pressure lubricant comprising a mineral lubricating oilhaving dispersed therein about 1% of the thio-ether formed by thecondensation of ethyl benzoate in the presence of thionyl chloride andcopper dust.

8. An extreme-pressure lubricant comprising a mineral lubricating oilhaving dispersed there: in about 1% of the thio-ether formed by thecondensation of ethyl phthalate in the presence of thionyl chloride andcopper dust.

9. An extreme-pressure lubricant comprising a .lubricant havingdispersed therein between 0.1% and 2% of a thioether having asubstituentgroup--COOX wherein X is a radical of the group consisting ofaliphatic radicals.

10. An extreme-pressure lubricant comprising a lubricant havingdispersed therein between 0.1% and 2% of a thioether each radical ofwhich contains a substituent-group-COOX in which X is of the groupconsisting of aliphatic radicals.

11. A lubricant comprising a lubricating oil having dispersed therein anextreme-pressure agent consisting of a thioether having asubstituen't-groupCOOX in which X is of the group consisting ofaliphatic radicals.

12. A lubricant comprising a lubricating oil having dispersed thereinbetween 0.1% and 2% of an extreme-pressure agent consisting of athioether each radical of which contains a substituent-group-COOX inwhich X is of the group consisting of aliphatic radicals.

ELLIOTT ALFRED EVANS.

